Tooth Positioning Appliance With Curved Interconnecting Elements

ABSTRACT

A removable, thin-shell tooth positioning appliance having a plurality of tooth-clasping elements for removably engaging attachments bonded onto selected teeth, with flexible curved interconnecting elements connecting the tooth-clasping elements on nearby teeth.

RELATED APPLICATIONS

The present application is a continuation of the Applicants' co-pendingU.S. patent application Ser. No. 14/566,474, entitled “Tooth PositioningAppliance With Curved Interconnecting Elements,” filed on Dec. 10, 2014,which is based on and claims priority to U.S. Provisional PatentApplication 61/914,832, filed on Dec. 11, 2013.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to the field of orthodontics.More specifically, the present invention discloses a tooth positioningappliance with curved interconnecting elements.

Statement of the Problem

A wide variety of orthodontic aligners have been used for many years inrepositioning teeth during orthodontic treatment. It should be notedthat the terms “aligner”, “positioner” and “tooth positioning appliance”are largely synonymous as used in the orthodontic field.

This type of orthodontic treatment typically involves separate toothpositioning appliances for the upper and lower teeth. The toothpositioning appliances fit over the teeth, covering nearly all of thefacial and lingual surfaces, and also most of the occlusal, or bitingsurfaces of the teeth. The early positioners described in the prior artwere made from a set of plaster models derived from three-dimensionalnegative dental impressions of the patient's teeth. The plaster dentalmodels were modified by cutting the teeth apart using a small jeweler'ssaw or rotary cutting discs and repositioning the plaster teeth in abetter, straighter, desired arrangement, and holding the teeth in thenew arrangement by using dental wax. The reset teeth molds provide thebasis for manufacturing the positioners. The resilience of the materialfrom which the positioner is made provides the energy to move the teethfrom their original position toward the new straightened position. Fromthe earliest disclosure of the tooth positioner, many of the proposeddesigns in the prior art have shown moving the teeth in a series ofincremental steps. Making a series of appliances is difficult if thetooth arrangement for each step must be made by hand using plaster andwax.

Starting in the early 1990's, digital technologies have begun to provideorthodontists with fundamentally new tools for delivering orthodontictreatment by fabricating tooth models in small but accurate incrementalsteps. Commercially-available CAD/CAM software can produce the desiredtooth models, from which a progressive series of appliances can bemanufactured. These tools include 3D imaging of the patient's dentition,and CAD/CAM (computer-aided design and manufacturing) systems forcreating virtual models in orthodontic treatment to then producecustomized orthodontic appliances.

An example of the successful orthodontic application of these digitaltechnologies is seen in the commercial service known as the Invisalign®program by Align Technology, Inc. of San Jose, Calif. The Invisalignprogram is largely based on U.S. Pat. No. 5,975,893 (Chishti et al.) andmany related patents, including U.S. Pat. No. 6,398,548 (Muhammad etal.). Invisalign tooth positioners are a progressive series of thin,transparent, U-shaped plastic appliances formed over computer-generatedforming patterns grown from a virtual model of the patient's dentalanatomy. The process for forming aligners uses a combination of vacuum,pressure and heat. This forming process is informally referred to withinthe orthodontic laboratory community as the “suck down” process.

In order to produce a series of Invisalign-type tooth aligners, atechnician first scans a patient's upper and lower model set to obtainCAD-manipulatable virtual models of a patient's dental anatomy. A modelset normally consists of one upper and one lower plaster model of theteeth, palate and gums. Once the virtual model of the originalmalocclusion has been obtained, a technician will then undertake stepsinvolving extensive manipulation of the virtual malocclusion. Thisinvolves extensive repositioning of the teeth according to acomprehensive and sequential procedure, ultimately arriving at afinished or ideal occlusion for that patient. The finished occlusion inthe virtual model is consistent with the complete repositioning of thepatient's upper and lower occlusion that would result at the end ofsuccessful conventional orthodontic treatment.

After the steps described above are accomplished, the technicianpossesses two versions of the patient's teeth available within thevirtual CAD environment. One version represents the originalmalocclusion and the other represents the ideal occlusion. In otherwords, the technician has the beginning and the end states.

The next step in the Invisalign process involves the creation of anincremental, progressive series of physical forming models. Each ofthese forming models represents a snapshot of the patient's futureocclusion at specific incremental steps along the patient's proposedtreatment sequence between the beginning and the end conditions asdescribed above. To accomplish this, the technician creates a virtual“first transition model” that sees a slight repositioning of all or mostof the teeth. This first transition model sees some or all of the teethbeing subtly moved from their original pre-treatment positions to avirtual first transition position that is in the direction of theirintended finished positions. Similarly, a second virtual transitionmodel is created that sees the virtual teeth being moved again slightlyfurther in the desired directions. The objective of the Invisaligntechnician is to create a series of progressive models, each biasedslightly further than the previous one, and each moving the teethslightly closer to their finished target positions. A final formingmodel will take the teeth from the series of transition positions andmove them into their final, desired positions.

Once such a series of virtual intermediate forming models has beencreated and a final forming model has been created by the Invisaligntechnician, the digital code representing each of the models in theseries is directed to operate a computer numerically-controlled (CNC)machine known as a rapid prototyping machine. Within a rapid prototypingmachine, the series of physical forming models are grown using any ofnumber of conventional processes, such as stereo lithography or 3Dprinting. The growing step results in the production of hard, physicalduplicates of each of the series of virtual intermediate models and thefinal model.

The next step of the Invisalign process sees each of the series ofphysical models being in turn mounted in a suck-down machine where acombination of pressure, heat and vacuum is used to form the actualseries of progressive aligners from plastic sheet material of a constantthickness. Once the series of progressive aligners are formed andtrimmed, they are sequentially labeled, packaged and shipped to theattending orthodontist. The orthodontist then schedules an appointmentfor the patient, at which time the aligners and instructions for theiruse are given to the patient. The patient is instructed to wear thefirst set of aligners for a period of time, typically two weeks. Afterthat, the first set is discarded and the patient transitions to the nextset of the series and so on.

The aligners serve to urge the patient's teeth to move according to thepositional biases created virtually by the Invisalign technician. Theteeth are progressively biased and urged to move in desired directionstoward their predetermined finished positions by the resilience of thepolymeric material of the aligner. In response to the gentle butcontinuous forces delivered by the aligners, certain physiologicalprocesses involving the creation and resorbtion of the bone supportingthe roots of the teeth are initiated. The net result is the slow,progressive orthodontic movement of the roots of the teeth through theunderlying bone toward desirable positions and orientations.

Physiologic processes occur when forces are applied to teeth, resultingin bone resorption and new bone apposition. Studies have shown that themost rapid tooth movement occurs when light gentle continuous forces areapplied to teeth. Conventional aligner appliances tend to apply heavierforces when the appliance is first placed on the teeth, and the forcesdecay away fairly rapidly after the appliance has been in place for aday or so. The reason for making many stages of aligners correspondingto very small incremental movements is to keep the forces lighter, andto re-establish the force when it decays by going on to the next alignerstage. Although in principle the use of many stages of aligners shouldallow the delivery of lighter more continuous forces, in practice thereare still problems with providing adequate tooth engagement and withkeeping force delivery within the desired physiological range.

Many conventional removable aligners are limited by their design and themechanical properties of the clear thermoplastic materials that arecurrently utilized. The clear polymeric materials make the alignernearly invisible, and that is a great advantage over fixed stainlesssteel hardware and metal braces. On the other hand, conventionalpolymeric materials used in forming aligners have a very limited abilityto flex. This is particularly a problem when aligning teeth that are notfairly well lined up in the beginning of treatment.

Even when very small movements during each stage are attempted, theappliance may fail to properly engage teeth that need to be movedbecause the appliance is not adequately flexible and is not designed toallow movement within the plane of the material. If a particular alignerfails to properly engage a tooth, then that tooth will not move to theproper place to engage the next successive aligner in the series. Theonly present solutions available when aligners fail to properly engage atooth are: (1) reduce the amount of movement attempted for thatparticular stage; or (2) place a larger bonded attachment on the tooth.Both of these solutions require reworking the computerized treatmentplan. If the plan is not revised, with each successive stage of theappliance, the fit of the aligners deteriorates, and after just a fewstages, it becomes obvious that the teeth are not moving according tothe original computerized treatment plan, forcing a revision of thetreatment plan.

Solution to the Problem

The present invention seeks to overcome the limitations of the lack offlexibility of the appliance material by providing a tooth-claspingelement for each tooth that is connected by curved interconnectingelements to the tooth-clasping elements of nearby teeth. The curvedinterconnecting elements are flexible enough to allow eachtooth-clasping element to remain firmly engaged in place. The flexibleproperties of the interconnecting elements are controlled by the choiceof materials, by the cross-section of the interconnecting elements, andby the shape of the interconnecting elements. The shape chosen in mostof the embodiments of the interconnecting element in the presentinvention is a small radius loop configuration, where the radius of theloop is preferably about half of the width of the tooth.

SUMMARY OF THE INVENTION

This invention provides a removable, thin-shell tooth positioningappliance having a plurality of tooth-clasping elements for removablyengaging attachments bonded onto selected teeth, with flexible curvedinterconnecting elements connecting the tooth-clasping elements onnearby teeth.

These and other advantages, features, and objects of the presentinvention will be more readily understood in view of the followingdetailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more readily understood in conjunction withthe accompanying drawings, in which:

FIG. 1 is a perspective view of a lower dental arch 10 with the presentappliance positioned above it. The U-shaped wire interconnectingelements 17 are shown on both buccal and lingual sides of the teeth 11.Dotted lines indicate the path the appliance would follow to be seatedin place on the teeth 11.

FIG. 2 is a front elevational view of an interconnecting element 17having flattened ends 18.

FIG. 3 is a side view of a portion of the appliance fitted on some ofthe teeth in the upper right quadrant.

FIG. 4 shows views from five different directions of a single tooth(upper right first premolar) with bonded attachments 12A and 12B, atooth-clasping element 15, and U-shaped wire-loop interconnectingelements 17 in place.

FIG. 5 shows a 3-dimensional view of a rectangular bonded attachment 12Awith the X, Y, and Z axes indicated.

FIGS. 6-9 provide views of three types of simple tooth movement in thetransverse plane. FIG. 6 illustrates an initial view of unmoved tooth,with CR and CC points located. FIG. 7 shows lingual root tippingmovement with crown center remaining stationary. FIG. 8 shows a buccalcrown tipping movement with center of resistance remaining stationary.FIG. 9 indicates horizontal transverse translational (bodily) movementwithout tipping.

FIG. 10 is a side view of an appliance fitted on some of the teeth inthe upper right quadrant. The appliance is similar to that shown in FIG.3, but a tooth has been extracted and other teeth are being moved toclose the extraction space. The tooth-clasping element of the teethadjacent to the extraction space on either side has been modified toinclude a straight arm extension of the buccal flange. The arm extendsover the gum line and includes a hook, or button, or other attachmentmeans for installing an elastic band to apply additional force to closethe space. Because the elastic band is attached near the center ofresistance of the tooth near the center of the root of the tooth, thetipping moment is reduced, thereby making it easier to avoid tipping thetooth while the space is closing.

FIG. 11 shows a perspective view of a lower arch dental model withanother embodiment of the appliance positioned above it. The applianceis made of a single piece of material, but localized regions of theappliance function as tooth-clasping elements and as flexible curvedinterconnecting elements. Dotted lines indicate the path the appliancewould follow to be seated in place on the model.

FIG. 12 shows a side view of a portion of the appliance in FIG. 11fitted on some of the teeth in the upper right quadrant.

FIG. 13 presents an enlarged view of FIG. 12 with added support ridges43 to the interconnecting elements and added support ridges 44 aroundthe bonded attachments.

FIGS. 14-21 show cross-sectional views of interconnecting elements witha variety of shapes for the added support ridges 43, 44.

FIG. 22 shows another embodiment of the appliance fitted on teeth in theupper right quadrant, similar to the view shown in FIG. 12. In thisembodiment the large curved loops of the interconnecting elements 41 arefolded over so they are in an inverted position. In this position theystill function in much the same way, but they are less likely tointerfere with buccal frenum attachments. The mechanics of the invertedloop tend to keep the root positions closer together as the loop isstretched open. It should be noted that the entire appliance, includingthe interconnecting elements 41, can still be fabricated as a singlepiece.

FIG. 23 is a modification of the embodiment shown in FIG. 12 in whichdifferent materials are used to fabricate the tooth-clasping elements 15and the curved interconnecting elements 42.

FIG. 24 shows a side view of another embodiment of the appliance fittedon some of the teeth in the upper right quadrant. This embodiment isalso a single piece appliance like that shown in FIGS. 11 and 12. Thedifference is the flange portion 16 of the appliance covering some ofthe gum tissue on the facial side (shown) and lingual side (not shown)and the interdental portion 52 of the flange function as the flexibleinterconnecting elements.

FIG. 25 shows a perspective view of a lower arch dental model withanother embodiment of the appliance positioned above it. The smallcurved flexible polymer interconnecting elements are shown between thetooth-clasping elements. Dotted lines indicate the path the appliancewould follow to be seated in place on the model.

FIG. 26 shows a side view of the appliance fitted on some of the teethin the upper right quadrant.

FIG. 27 shows views from five different directions of a single tooth(upper right first premolar) with bonded attachments 12A and 12B, atooth-clasping element 15, and small, curved flexible interconnectingelements 30 in place.

FIG. 28 is a cross-sectional view of a dental model 10 of the lowerteeth with the plane passing transversely through the centers of thesecond premolar teeth 11. The tooth-clasping elements on the lowersecond premolar teeth are shown in place, seated on the teeth of thedental model. The external surfaces 13A and 13B of the teeth in themodel, on both the buccal and lingual sides of the teeth, between thegum line and the bonded attachment have been moved inward (toward thecenter of the tooth) a small distance, as indicated by the dotted lines.

FIG. 29 is a detail cross-sectional view of the dental model with thetooth-clasping elements corresponding to FIG. 28.

FIG. 30 is a perspective view of a lower dental arch 10 with anotherembodiment of an appliance having longer interconnecting elements 17Aand 17B on both the buccal and lingual aspects of the appliancesegments.

FIG. 31 is a front view of another embodiment of the appliance withlonger interconnecting elements 17 on the buccal aspect of the appliancesegments.

FIG. 32 is a bottom view corresponding to FIG. 31.

FIG. 33 is a front view of yet another embodiment of an appliance havinglonger interconnecting elements 17 between the tooth-clasping elements15 on individual teeth.

FIG. 34 is a side view corresponding to FIG. 33.

FIG. 35 is a right side view of another embodiment of an appliance onthe upper right teeth with an interconnecting element 17 connected fromthe posterior appliance segment near the first molar tooth to theanterior appliance segment directly above the central incisors.

FIG. 36 is a right side view of another embodiment of an appliance onthe upper right teeth with an interconnecting element 17 made of wireconnecting the posterior appliance segment with the anterior appliancesegment.

DETAILED DESCRIPTION OF THE INVENTION

Turning to FIG. 1, the present tooth positioning appliance includes thefollowing major elements: (1) bonded attachments 12A, 12B bonded to thelingual or buccal surfaces of selected teeth 11; (2) tooth-claspingelements 15 removably engaging the bonded attachments 12A, 12B; and (3)curved interconnecting elements 17 extending between adjacenttooth-clasping elements 15. In particular, the tooth-clasping elements15 include recesses designed to fit over projecting elements or buttonscalled “bonded attachments” 12A, 12B that are bonded directly to theteeth. The bonded attachments 12A, 12B are not typically removable bythe patient during the course of active orthodontic treatment.

It is desirable to have the tooth-clasping elements 15 on the frontteeth made of a clear polymeric material. Currently, several differentplastic materials including urethanes and polycarbonates can bethermoformed over tooth models to produce the desired tooth alignmentappliances. The material can be any suitable material. It should also benoted that the tooth-clasping element 15 can be a separatelymanufactured part or a functional region of a single-piece appliance.

The bonded attachments 12A, 12B are typically bonded to the buccal orlingual surfaces of selected teeth 11, as shown in FIG. 1. For example,the bonded attachments can have a substantially rectangular shape withparallel sides, as shown in FIG. 5, although it is to be understood thatthere are many possible shapes for bonded attachments that would besuitable. The bonded attachments 12A, 12B are utilized for two purposes:(1) the bonded attachments 12A, 12B increase the retention of thetooth-clasping elements 15 to the teeth 11, (or in other words, theappliance is less likely to become dislodged from the desired locationon the teeth); and (2) the bonded attachments 12A, 12B have a shape thatallows the tooth-clasping elements 15 to transmit desired forces to theteeth in three-dimensions, thereby providing control over root movement.In the rectangular bonded attachment 12A shown in FIG. 5, the parallelouter edges of the attachment 12A provide surfaces for positiveengagement to allow forces to be applied to the teeth to accomplish rootmovement under control. Inner surfaces of an attached projection such ascan be provided by grooves or special shapes can also provide thiscontrol. Grooves or special outside shaping can help guide thetooth-clasping element into position. The bonded attachments can bepre-made of any suitable material including dental composite, clear ortooth-colored ceramic materials, or any suitable clear plastic material.The attachments 12A can be bonded to the teeth using conventionalbonding techniques and adhesives that are well-known in the artincluding the steps of mildly acid-etching the enamel prior to bracketplacement. A technique well known in the art called indirect bonding canbe utilized, with a pre-formed guide made of flexible material holdingthe attachments in the desired position while the adhesive is curing toensure accurate attachment placement on the teeth. The bondedattachments can alternatively be fabricated out of dental compositeusing pre-made hand-held molds for one tooth at a time placement,commercially available for this purpose. A third alternative is toutilize a mold made using 3D CAD/CAM technology, where the shape and thesize of the bonded attachments are planned in the computer and a modelof the entire dental arch with attachments in place is printed using a3-D printer. From this model, a mold is made from which to fabricate andplace dental composite attachments in precisely the right locationdirectly on the teeth.

Preferably, the tooth-clasping elements 15 include a hole of precisedimensions (e.g., a rectangular hole) through which the bondedattachment 12A, 12B projects to removably engage the tooth-claspingelement 15. Alternatively, a recess on the inside of the tooth-claspingelement 15 of exactly the same shape and size as the bonded attachment12A, 12B should work equally as well, particularly if the tooth-claspingelement 15 is printed, because of the ability of the printing process toproduce a more precise fit than can be obtained by thermoforming.

The tooth-clasping elements 15 are be attached to flexible curvedinterconnecting elements 17 of many types, as illustrated in thedrawings. In some embodiments of the present invention, the appliancesare made of one piece of material, and the tooth-clasping element andthe flexible interconnecting elements are all part of a monolithic wholeunit. Functionally, different regions of the single-piece positionerserve as the tooth-clasping element 15 and the flexible interconnectingelements 17.

It is anticipated that the improved tooth positioners of the presentinvention will be produced by planning and designing the appliancesusing computerized 3-D CAD/CAM software. Many off-the-shelf softwareprograms are currently available that are capable of this function. Overthe long-term, it will be beneficial to write new software thatintegrates easily with the skill levels of orthodontist end-users, tosimplify their use of the product. Open-source software that can bemodified is currently available to perform this function. The standardsurface mapping computer algorithms define the surface as a series oftriangles. The actual physical production of the appliances can beaccomplished by vacuum-forming thermoplastic materials over modelsproduced digitally and combining the thermoformed portion of theappliance with the other necessary elements. This step is followed byusing computer automated trimming technologies such as CNC milling orlaser cutting. In particular, the clear tooth-clasping elements could beproduced by vacuum thermoforming. In the single-piece embodiments of thepresent invention, the tooth-clasping elements and the flexibleinterconnecting elements could all be vacuum thermoformed together.

Alternatively, positioners can be made without first producing 3D modelsvia 3D printing. A big advantage of direct 3D printing is that morecomplex shapes could be more easily printed, and almost no trimming ofexcess material would be necessary, saving time and avoiding wastedmaterial. Some new 3D printers can print more than one material at thesame time. The flexible interconnecting elements could be printed alongwith the tooth-clasping portion, and they could be made of differingmaterials. The materials can be blended or intertwined which will avoidthe need for a separate attachment step in manufacturing. Another optioninvolves direct CNC milling of the appliances or portions of theappliances from a block of plastic material. It is anticipated that thepresent appliances will be made in a series. Each appliance will moveteeth a small distance, and then successive stages will continue themovement in small steps toward the desired goal. Each stage of theappliance can be fabricated in such a way as to fit over the teeth wherethey ideally should be for the next step or stage. The appliance willhave to be deformed to fit over the teeth in their present position. Thetooth-clasping elements 15 should fully engage each tooth. If thepatient wears the appliance for a sufficient number of hours each day,after the appliance has been worn for a few weeks, the resiliency of theappliance will carry the teeth toward the desired position for the endof that particular stage. Then the next stage of the appliance will beplaced on the teeth and will carry the teeth another prescribeddistance, and so on until the desired final position is reached. It islikely to be necessary to take new impressions or new digital scansevery few stages to keep the appliances fitting accurately as theprocess of straightening the teeth progresses.

Many of the accompanying drawings show tooth-clasping elements fittedover individual teeth. If adjacent teeth are aligned, and it isanticipated that this will routinely occur during later stages oftreatment, it is not necessary to generate a separate tooth clasp foreach individual tooth in each stage. Groups of adjacent teeth may havetooth-clasping portions combined if these teeth are well aligned witheach other. It may also be desirable in certain stages of treatment tocombine teeth together in groups to be used as anchorage units, toprovide better control over the movements of other groups of teeth. Inthese cases, the present appliance can be divided into multiplethin-shell segments. Each thin-shell segment can be designed to engage agroup of adjacent teeth (i.e., one or more adjacent teeth). However,only select teeth in each group are equipped with bonded attachments12A, 12B to engage corresponding tooth-clasping elements in thethin-shelled segment. This concept is somewhat similar to that used inorthodontic treatment with fixed braces, especially when extractionspaces are being closed and is well-described in the prior art. It isalso possible to combine features of several of the embodimentsdescribed in this disclosure into one appliance to accomplish certaintypes of movements more efficiently.

To summarize, the embodiment of the present invention shown in FIGS. 1-4includes clear tooth-clasping elements 15 fitted over teeth 11 to whichbonded attachments 12A, 12B have been placed on both the buccal andlingual sides. The tooth-clasping elements 15 are connected togetherusing flexible U-shaped interconnecting elements 17 made of wire loopsattached to the flange (or extension) 16 of the tooth-clasping element15 that covers part of the gum tissue adjacent to the teeth on both thebuccal and lingual sides. FIG. 2 is a front elevational view of a wireinterconnecting element 17 having flattened ends 18. The wire can bemade preferably of nickel-titanium shape-memory wire, heat treated tothe desired shape and of the appropriate dimensions, although othersuitable materials can be utilized. The clear tooth-clasping elements 15will be nearly invisible on the teeth 11, and the wire interconnectingelements 17 will go over the gum tissue in a less visible zone. Thisembodiment may have the greatest flexibility, and it is thereforeanticipated this will be used to correct tooth rotations and crowding insituations where other embodiments cannot be used. This embodiment maybe somewhat more difficult to manufacture because of the multiple partsand materials. The curved interconnecting elements 17 can also bemounted in an inverted position. Although the loops will be in a morevisible location, inverted loops may be preferred for posterior teeth.

In particular, the bonded attachments 12A, 12B are preferably placed onthe buccal and lingual aspects of all teeth, upper and lower, althoughthere may be some instances where not all teeth have all theattachments. In the illustrations, rectangular bonded attachments areshown. The tooth-clasping elements 15 are preferably made of a clearplastic material or other suitable material cover most of the facial,occlusal, and lingual surfaces. The tooth-clasping elements adapttightly to and conform to the outer contours of the teeth and the bondedattachments.

There can optionally be an open window through which the bondedattachment 12A, 12B projects, or the bonded attachment can be coveredcompletely by the appliance. Either way, the tooth-clasping element 15adapts tightly to the bonded attachment 12A, 12B and the portion of thecrown of the tooth covered by the tooth-clasping element so as to allowforces transmitted to the tooth-clasping element 15 to be directlytransmitted to the tooth. The forces can be in any direction needed tocorrect the malocclusion. The curved interconnecting elements 17 arepreferably made of wire with flattened ends to prevent the wire frombeing pulled out of the material covering it that forms the bond of thewire with the tooth-clasping element 15.

This embodiment of the present invention includes a removableorthodontic appliance that will be worn by an orthodontic patient afterthe bonded attachments 12A, 12B have been placed on the teeth by theorthodontist, preferably using a method that allows great precision suchas the aforementioned indirect bonding method or a computer-generatedmold. The appliance will be made in multiple stages, each one moving theteeth in small increments toward a final desired goal envisioned by theorthodontist and planned in the computer using commercially-availableCAD/CAM software designed for this purpose. This embodiment is mostlikely to be used in the early stages of treatment when the teeth are intheir most crowded or irregular state. The flexibility of Ni-Ti wires isgreater than the flexibility of any of the other materials utilized onthe interconnecting elements in other embodiments disclosed herein.Therefore, this should allow complete engagement of the tooth-claspingelements in more complex orthodontic cases than have previously beentreatable with removable positioner appliances.

The present appliance may be formed from a model of the patient's dentalanatomy made of conventional plaster or a dental stone model, made bypouring the plaster or dental stone when it is uncured (wet) into animpression made of alginate, polyvinyl siloxane, silicone, polysulfiderubber or other suitable dental impression material. After the plasteror stone has cured (dried), the excess material is trimmed using aconventional rotating wheel model trimmer so the base is flat and theedges of the base are smooth. Alternatively, the dental model can beobtained by using conventional digital scanning techniques of the teethdirectly in the mouth using a commercially-available digital intra-oralscanner, or the plaster or stone model can be scanned using acommercially available digital model scanner, or the impression itselfcan be scanned using a digital scanner or a computerized tomographyscanner (CT). From the digital data obtained by the scan, athree-dimensional model can be produced using a commercially availablestereo lithographic printer, or a commercially-available rapidprototyping printer, or a model can be produced using acommercially-available CNC milling machine operating on any suitablematerial, most likely a plastic block.

The three-dimensional images of the teeth (anatomic portion) areattached to the base of the dental model. The images of the teeth(virtual teeth) are the same size and shape and in the same relativelocation to each other as the real teeth in the mouth of the dentalpatient. In other words, the model of the teeth is an accuraterepresentation of the real teeth in the mouth of the patient.

The bonded attachments 12A, 12B serve the purpose of providing analtered shape attached to, but different from the surface of the tooth.The bonded attachments are vital for retention of the removableappliance in the correct location on each tooth. The bonded attachmentsalso allow the tooth-clasping element to transmit forces to the tooth soas to provide complete control over the position of the tooth in threedimensions. The bonded attachments protrude from the surfaces of theteeth, and in this particular illustration, the attachments havestraight sides to properly orient the tooth-clasping elements in adesired position. As a general rule, the bonded attachments will beplaced on the teeth prior to beginning any tooth movement.

The tooth-clasping elements 15 are formed utilizing an accurate model ofthe teeth 11. As shown in FIG. 1, there are separate tooth-claspingelements 15 to fit over each tooth in the arch, with shapescorresponding to the shape of each tooth. It can be seen that there arespaces between each tooth-clasping element (even if the teeth themselvesare touching). The inner surface of the tooth-clasping element should bealmost exactly the same shape and dimensions as the outer surface of thetooth to which it will be applied. Because the material from which thetooth-clasping element 15 is made has some thickness, the outer surfaceof the tooth-clasping element 15 will have greater dimensions but asimilar shape corresponding to the inner surface of the tooth-claspingelement. The outer surface is essentially a slightly enlarged orinflated version of the inner surface. The tooth-clasping element 15typically has components that touch the tooth 11 on the buccal (outer),occlusal (top of bottom teeth, and bottom of top teeth) and lingual(inner) surfaces.

The tooth-clasping element 15 may also include a clear flange (orextension) 16 as an integral part of the tooth-clasping element 15. Theflange 16 generally extends over the gum tissue of the patient on thefacial and lingual sides of each tooth by a distance of approximately 2to 3 mm, although the flange does not have to project that far. Theflange 16 does not typically contact the gum tissue. There is clearanceof at least 0.5 to 1 mm.

The flange 16 can serve as the attachment area for the flexible curvedinterconnecting elements 17. It is also possible to attach the flexibleinterconnecting element 17 directly to the main body of thetooth-clasping element 15, for example in the area between the bondedattachment 12A, 12B and the gum line without utilizing the flange. Thismay be particularly desirable on posterior teeth where the need to hidethe loop behind the lips would not be as much of a cosmetic concern. Theadvantage this would provide is to reduce the risk of interferencebetween the loops and the buccal frenum attachments. There would be asmaller vertical dimension to the appliance with the same sized loops.

In this particular embodiment, each interconnecting element 17 is aU-shaped wire, preferably made of heat-treated Ni-Ti shape memory wire.The U-shaped interconnecting element 17 extends outward slightly toavoid contact with the gum tissue, and maintains an open space 19between adjacent tooth-clasping elements and allows range of movement.The exact dimensions of the U-shaped loop, and the thickness andheat-treatment of the wire to achieve the desired shape-memoryproperties can be varied to produce the desired physiologic forcesapplied to the tooth-clasping elements, and therefore the desired forcesapplied to the teeth. Alternatively, the flexible interconnectingelement could be made of any suitable material. In this particularembodiment, the attachment means of the interconnecting element 17 tothe tooth-clasping portion is not shown, primarily because it istransparent, and therefore would not be readily visible.

It should be noted that the interconnecting elements 17 have flattenedends 18 in the embodiment shown in FIGS. 1 and 2. If the flexibleinterconnecting element 17 is made of wire, the end of the wire is bentapproximately 90 degrees and is placed in a hydraulic press to flattenthe end 18, possibly with some small serrations pressed into the metalwire. The bent ends prevent the wire from being pulled out of the clearplastic that encases them. There are several conventional methods bywhich the interconnecting element could be attached to the flange of thetooth-clasping element. (1) Clear cold-cure acrylic could be appliedover the wire in much the same way that wire elements are attached tothe plastic of retainers commonly used in orthodontics today. (2) Thesame plastic material from which the tooth-clasping element is madecould be applied in a molten state using a glue-gun nozzle and couldcover the wire with a thin layer. This technique could be automated, andthe nozzle could be robotically controlled on an assembly line. (3) Asmall plastic panel of approximately the same size as the flange of thetooth-clasping element could be placed over the flexible interconnectingelement ends, and while being held in place, a focused ultrasonic welderwaveguide horn could be placed adjacent to the two pieces of plastic tofuse the flange and the small panel together.

Alternatively, rather than flattening the ends of the wire segments,other means could be employed to prevent the wire from pulling out ofthe plastic, such as a zigzag in the wire, or bending the wire into anL-shape, or doubling it back on itself to form a T-shape, or forming thewire into a small circle, etc.

It should be noted that larger segments of wire could be used than theshort segments shown in FIGS. 1 and 2. A longer segment of wire,containing multiple loops could be used to connect multipletooth-clasping elements together. The wire could be attached usingvarious means, including: (1) direct cementation using a composite orplastic cement, covering the wire; or (2) the tooth clasping elementscould be printed or formed in such a way as to have a groove or recessto receive the wire, and the wire could even snap into place if thegroove is designed so that the opening to receive the wire is slightlysmaller than the wire and the portion of the groove where the wire isintended to reside. The groove can be square or rectangular incross-section to receive a wire which is square or rectangular incross-section. The wire could even be one piece with multiple loops init.

FIG. 3 shows a right side view of some of the upper teeth with a portionof the same type of removable appliance shown in FIG. 1 installed onthese teeth. Reference number 11A designates the root of the upper rightcuspid tooth. The mesial surface 11B of the crown of the upper rightcuspid tooth can be seen just sticking out beyond the mesial edge of thetooth-clasping element. FIG. 4 shows views from five differentdirections of a single tooth (upper right first premolar) with bondedattachments 12A and 12B, a tooth-clasping element 15, and U-shapedwire-loop interconnecting elements 17 in place.

Note the size of the bonded attachments 12A varies with the size of theteeth. The bonded attachments in this view protrude through holes in theclear tooth-clasping elements. The holes are of the same size and shapeas the bonded attachments. As discussed earlier, it is not necessary touse rectangular bonded attachments, nor is it necessary to use holes inthe tooth-clasping elements to allow protrusion of the bondedattachments through the tooth-clasping elements. A simple recess in theinner surface of the tooth-clasping element precisely corresponding tothe size and shape of the chosen bonded attachment geometry will stillprovide the necessary clasp function that is vital to the properfunctioning of this appliance. Note there are spaces 19 between each ofthe tooth-clasping elements 15 even though the teeth themselves may bein contact. The space prevents the tooth-clasping elements frominterfering with each other. FIG. 4 provides an upper right firstpremolar tooth viewed from five different angles showing a singletooth-clasping element 15 with interconnecting elements 17 attached asthey would be positioned to reach toward adjacent teeth.

FIG. 5 shows a perspective view of a bonded attachment 12A, with thethree axes of tooth movement intersecting within the center of the crownof the tooth (not shown) on which the bonded attachment is fixedlymounted. The x-axis in this case is a horizontal axis in theanterior-posterior direction. The y-axis is a vertical axis. The z-axisis a horizontal axis in the transverse direction. The bonded attachmentcan be positioned away from the center of the crown of the tooth. Whenforces act on the bonded attachment, depending on the direction of theforce, the force produces a moment, which may cause a more complexmovement of the tooth than is at first anticipated.

FIGS. 6-9 illustrate three different transverse movements, along thez-axis, as shown in FIG. 5 (i.e., not in the X-Y planes of the bondedattachments.) An upper right first premolar tooth is shown in all thedrawings, viewed on the distal side. All of these movements require theresetting of teeth from the original position to a new desired position,either in a digital 3-dimensional file representing the positions ofteeth, or using a dental model, whether resetting teeth manually, orwhen generating 3-D models from computerized digital files. FIG. 6provides a reference view. FIG. 7 shows lingual transverse movement ofthe root with the center of the crown (CC) staying in the originalposition. The movement is a root tipping movement that is relativelydifficult to accomplish, even when using fixed braces. For thismovement, it would be desirable to use a trans-palatal bar to provideadditional support to assure the desired movement. The movement isaccomplished primarily by vertically moving the buccal and lingual sidesof the teeth with the bonded attachments, although it can be seen thatthere are small transverse movements of the tooth surface taking placealong with the bonded attachments.

FIG. 8 shows buccal transverse movement of the crown with the center ofthe root (or center of resistance, CR, to movement of the tooth) stayingin the original position. This tipping movement of the crowns of theteeth is relatively easy to accomplish, because the roots of the teethnaturally tend to remain in place. The movement is accomplished by acombination of movements of the buccal and lingual surfaces of the teethalong with the bonded attachments. In this drawing, it can be seen thatthere is approximately the same amount of vertical and transversemovement of the bonded attachments taking place, although the transversetipping movements of the crown tend to naturally occur when opposingvertical forces are applied to the crowns of teeth, because of theresistance of the bone surrounding the roots.

FIG. 9 shows buccal or lingual transverse movement of the entire tooth,with the center of resistance (CR) and the center of the crown (CC)moving exactly the same distance and in the same direction. There is notipping of the tooth taking place. This type of movement requires bondedattachments, with very good engagement of the tooth-clasping elementwith the flat top and bottom surfaces of the bonded attachments toprevent the tooth from tipping.

FIG. 10 shows an embodiment of the present invention that includes alocalized extension of the flange 16 of the tooth-clasping element 15 onselected teeth to produce what is essentially an arm 70 for theattachment of stretchable elastic members 71 (e.g., rubber elasticbands, made of any suitable material). For instance, if a tooth has beenextracted as part of the orthodontic treatment plan, the closure of thespace while keeping the tooth roots parallel on either side of theextraction space (avoiding tipping the crowns of the teeth into theextraction site) has typically been a severe problem when usingremovable orthodontic appliances in the past. This is also a problemwith fixed braces on teeth. One of the solutions routinely used withfixed braces is to place a rigid arm with a retentive hook on thebrackets (an element commonly used with fixed braces) on either side ofthe extraction space to allow the use of elastic bands to help close thespace. The center of resistance for each tooth is located approximatelyin the center of the root of the tooth. Placing the attachment point forthe elastic band very close to the center of resistance of the toothreduces the tipping moment as the force from the elastic is applied. Theroots tend to stay more parallel when this method is used to close thespace. In the same way, the flange 16 of the tooth-clasping element 15can be extended to a point close to the center of resistance of thetooth, and an elastic band 71 can be utilized in the same way. If thereare arms on both the buccal and lingual side of the teeth, the forceswould be parallel, and the rotational moment present with a band 71 onlyon the buccal side would be cancelled. As a practical matter, it wouldbe uncomfortable for the dental patient with a long appliance armcovering the gum tissue on the lingual side of the teeth to wear such arubber band, although perhaps not impossible under certaincircumstances. It depends on the curvature of the palatal tissue.Another possible use might be where root movement is desired, such as toupright a tipped tooth, but where there is no interdental space. Toavoid tipping teeth that we do not want to tip, a group of teeth couldserve as the anchor.

FIGS. 11 and 12 show an embodiment formed from a single piece of clearvacuum-formed or printed material. Functionally, the flexible plasticinterconnecting elements 40 may not have the flexibility of wireinterconnecting elements, but they will be far easier to manufacture ifthe appliance is printed, and the loops will be less visible. It isanticipated that the flexibility of the clear plastic curvedinterconnecting elements will be sufficient to make the applianceworkable without resorting to the complex manufacturing and assemblyprocess required to utilize wire loops as in the first embodiment. Ifthe appliance is thermoformed and then cut, the instruction set forcomputerized mill cutting or laser cutting will be complex.

This embodiment utilizes the same bonded attachments 12A, 12B as theother embodiments. The removable positioning appliance is in two pieces,upper and lower. Each arch appliance is fabricated as a single pieceappliance with regions that function as tooth-clasping elements 15 andcurved, flexible interconnecting elements 40. The regions of theappliance that engage the teeth and function as tooth-clasping elementsare almost identical in size shape and form to those of the previousembodiments. The regions 40 of the appliance that serve the function ofthe flexible interconnecting elements are curved, and are approximatelythe same overall size as the U-shaped wire connecting elements of thefirst embodiment. Functionally it is almost identical to the firstembodiment, except the plastic loop is not as flexible or as strong as awire loop. This embodiment can be made as a thermoformed appliance overa series of tooth models, much like currently-marketed aligners, buttrimming away the excess material may be more difficult. It can beaccomplished using a CNC milling cutter, or a laser cutter, but willrequire more complex programming than is needed for currently usedaligners, where only the edge along the gum line needs to be trimmed.Alternatively, the entire apparatus can be 3-D printed and it is likelythat is the way the industry will turn once non-toxic printable plasticsbecome available.

The curved interconnecting elements can be a relatively flat, U-shapedribbon made of plastic or metal, for example. However, FIGS. 13-21illustrate that the physical properties of the curved interconnectingelements can be modified by the placement of reinforcing ribs or ridges43, 44 to change the cross-section of the interconnecting elements 40.The ribs 43 strengthen the U-shaped loops and can change the torsionaland flex properties of the loops. The ribs 44 can extend beyond theloops onto the bodies of the tooth-clasping elements 15 to increase thestrength of the tooth-clasping elements, especially in the central areasof the clasps 15 where they engage the bonded attachments 12A, 12B. Itis relatively easy to manufacture these strengthening ribs 43, 44 if theappliances are printed using a 3-D printer. In addition, theinterconnecting elements are not necessarily flat, but rather could haveany desired cross-sectional shape (e.g., circular, oval, tubular, amulti-strand cable, or a composite structure).

FIG. 13 is an enlargement of a portion of the appliance shown in FIG.12. The outer edge of the flexible interconnecting elements includereinforcing ridges 43 that will be printed into the material forming theinterconnecting elements. Note that the ridges 43 extend onto the flangesection of the tooth-clasping elements and also onto the maintooth-contacting portion of the tooth-clasping elements. On one tooth,in this case the upper right canine tooth, the reinforcing ridge extendsto and becomes continuous with a reinforcing ridge 44 that surroundsentirely the bonded attachment on the buccal surface of that tooth. Thepurpose of the reinforcing ridges is to add strength and to control theflex properties of both the tooth-clasping elements and the flexibleinterconnecting elements. It is to be understood that this disclosuredoes not limit the reinforcing ridges 43, 44 to this particular locationor configuration. The reinforcing ridges can be located anywhere theyare needed to add strength and to control the flex properties of thetooth-clasping elements and the flexible interconnecting elements.

FIGS. 14-21 illustrate several possible configurations for reinforcingridges that can be placed where they are needed on the flexibleinterconnecting elements or on tooth-clasping elements. Thesereinforcing ridges can be any suitable cross-sectional shape. FIG. 14shows two rectangular projections to form a C-shape. FIG. 15 shows asingle rectangular projection to form a T-shape. FIG. 16 shows doublerectangular projections. FIG. 17 shows two rectangular projections toform an I-shape. FIG. 18 shows two tapered projections to form aC-shape. FIG. 19 shows a single tapered projection to form a T-shape.FIG. 20 shows double tapered projections. FIG. 21 shows double taperedprojections on each side to form an I-shape.

The embodiment in FIG. 22 utilizes interconnecting elements 41 in aninverted U-shape. The inverted loop geometry may be better for keepingfavorable forces applied to the teeth to minimize tooth tipping duringspace closure. Conversely, the tooth-clasping elements may be moredifficult to place on the teeth if the loops are stretched open when theloops are inverted. In this embodiment, if produced by usingvacuum-formed thin-shell plastic, the appliance can be fully fabricatedwith the loops in the normal configuration. After completion, the loopscan be heated and flexed downward to assume their reverse configuration.This embodiment should become easily mass-producible using computer 3-Dprinting technology, and the inverted configuration should not require aseparate step for loop flexion. The first embodiment shown in FIGS. 1-4using wire interconnecting elements can also be manufactured with thewire loops in an inverted position, because a wire loop embodiment maybe better suited for closing interdental spaces.

Returning to FIG. 22, this type of appliance can also be made from athermoformed sheet by reheating the loops of the interconnectingelements 41 and flexing them downward into the inverted position. Anelectric heat gun with a blower, or an ultrasonic welder could be usedto heat and re-form the thermoplastic material. If the appliance isprinted, it can simply be printed in the inverted position. Theappliance does not extend as deeply into the buccal vestibule, andtherefore would not be as likely to cause irritation of the tissue ofthe cheek or gum tissue. It also conveys a mechanical advantage. If aloop is stretched open, such as when there is a space between teeth youare trying to close, there is not as much pressure placed to move theroot apices closer together. If the loop is inverted, and the loop isstretched open, it tends to move the roots closer together. This sameinverted loop geometry could be considered in the first embodiment,although you would not want to bend the wires downward. They should bemounted in the inverted position in the beginning.

The embodiment in FIG. 23 involves a modification of the materialsutilized in forming positioner appliances and could be applied to any orall of the embodiments of the present invention disclosed herein. If a3-D printer is utilized to manufacture a tooth-positioning appliance, wecan take advantage of the current capabilities of some of the newerprinters currently available. Multiple print nozzles can print more thanone material with each pass of the printer over a given location. Withthis capability, we can print an appliance made entirely of onematerial, or we can print an appliance with blended or mixed materials,or we can print an appliance with some portions made of one material,and some portions made of another material. This capability will allowcertain regions of the appliance to have greater or lesser flexibility,depending on the elastic modulus of the materials chosen for thatparticular region of the appliance. In the embodiment disclosed in FIG.23, the tooth-clasping elements 15 are made of one material, while thecurved interconnecting elements 42 are made of another material. Theappliance will be printed as one monolithic whole, and the componentswill not need to be assembled or attached in a fabrication sequence. Theprinter will print one portion of the appliance and will go right on toprint the other portion in a continuous motion as it is laying down theappliance layer by layer. The junction of the two materials can be asimple butt-joint junction where one material ends and another begins,or the junction can be a more complex intertwined zone with twomaterials interconnecting in such a way as to make the junctionstronger, and more resistant to pulling apart. The two materials canhave differing properties, such as elastic modulus, color, translucency,clarity, and strength such as yield strength, tensile strength, breakingstrength, etc. The junction of the two materials may be stronger if theprinter is programmed to mix or intertwine the materials in a briefjunction zone.

The flexibility of the interconnecting elements can be varied dependingon the type of malocclusion problem to be solved. In the early stages oftreatment a very flexible interconnecting element material can be chosento make it easier to engage a severely rotated tooth or a significantlytipped tooth. In later stages of treatment, the loops can be stiffer forbetter control over final tooth position just as the wire sizes arecurrently varied with the stage of treatment when fixed braces are used.The materials can also be chosen so that flexible materials are used forsome interconnecting elements and stiffer interconnecting elements areused for other interconnecting elements.

In the embodiment shown in FIG. 12, the U-shaped interconnecting element40 is made of the same clear material that forms the tooth-claspingelements 15. In other words, the appliance in FIG. 12 is a one-piecemonolithic structure. In contrast, the appliance shown in FIG. 23 ispreferably fabricated in one piece by using a 3-D printer that iscapable of printing more than one material at a time. The tooth-claspingelement 15 is preferably made of a clear material, and theinterconnecting element 42 is preferably made of a different material,perhaps with a differing elastic modulus to control the flex propertiesof the curved loop. Because of the way the printer prints using multipleprint nozzles, it is possible to gradually blend the materials into oneanother at the junction where the two materials join. It is unnecessaryto attach the two portions.

The embodiment shown in FIG. 24 is formed of a single piece of materialthat is clear as it covers the anterior teeth. It can be manufactured bythermoforming a sheet of plastic material over a model of teeth, or itcan be printed using a 3-D printer. There are no separately manufacturedinterconnecting elements as in the first embodiment. In its simplestembodiment, a single-piece tooth positioning appliance can bevacuum-formed over a plastic model. Flanges 16 of the appliance extendover the gum tissue. A difference in this embodiment is the flange 16 ofthe appliance also covers the interdental area including the interdentalpapillae, not just the gum tissue over the roots of the teeth as in theother embodiments of the present invention. Cuts are made between eachtooth through the plastic shell material, but they do not entirelyseparate the shell into individual tooth-clasping elements. The cut-awayarea 51 between the teeth ends near the gum line in a small radius archforming a U-shaped interconnecting element 52. The region of theappliance consisting of the flange portion of the appliance, includingthe flange area between the teeth covering the interdental papillae areaadjacent to the interdental cuts 51 serves the same function as theinterconnecting loop-shaped element 17 between two adjacenttooth-clasping elements in the earlier embodiments. Without the flangeextension of the appliance over the gum tissue there would not besufficient material to provide the needed flexibility for theinterdental portion of this appliance to serve the function of theflexible interconnecting elements as shown in the third embodiment. Ifthis appliance is printed using a 3-D printer, the same basic shape andsize of the appliance as in the thermoformed version would be produced.Rather than making cuts in the material to produce the interdentalvoids, the printer would simply not print the areas where thethermoformed appliance is cut away.

Alternatively, the embodiment depicted in FIG. 24 can be fabricated byremoving some of the appliance material to make the appliance moreflexible. There are two ways this material can be considered to be“removed.” First, if the appliance is made by thermoforming a sheet ofmaterial over a model, then a portion of that material can be removed bycutting it away using a CNC milling machine or a CNC laser cutter.Second, if the appliance is fabricated by a 3-D printer, then selectedportions of the coverage of the plastic over the teeth will not beprinted, leaving spaces where the coverage is chosen to be absent. Theembodiment shown in FIG. 24 is much like the embodiment in FIGS. 11 and12, in that both embodiments can be made of a single piece of materialcovering each dental arch. The flange material on the facial and lingualsides of the teeth covering the gum tissue area, and the additionalflange material covering the interdental area, serves as the flexibleinterconnecting element. This additional flange material covering theinterdental gum tissue area (specifically covering the interdentalpapillae) is shown only in FIG. 24 but it is to be understood that itcould be present in any of the embodiments described herein if there isnot a need for a separate tooth-clasping element for each tooth.

In some stages of treatment using an appliance system, one may use theembodiment from FIGS. 1-4 between two adjacent teeth, the embodimentfrom FIGS. 11-12 between the next two teeth, and possibly the embodimentfrom FIG. 24 between the next two teeth. In later stages of treatment,as the teeth become better aligned, there will be groups of teethcombined together into units where there are no interconnectingelements. This combining of the teeth into groups is shown in a separaterelated disclosure of a space closing appliance. In FIG. 24 there are noadded curved loops to serve as the flexible interconnecting elements asin FIGS. 11 and 12. The flange material serves as a smaller loop orinterconnecting element in FIG. 24. This embodiment is simpler andsmaller than FIGS. 11 and 12, and could still be more effective forsmall movements than a conventional tooth positioning appliance as isnow manufactured by several companies.

FIGS. 25-27 show an embodiment having clear tooth-clasping elements 15with interconnecting elements 30 that are U-shaped in horizontal planesextending outward from the tooth-clasping elements. In other words, eachtooth-clasping element 15 is connected to the adjacent tooth-claspingelement using short flexible U-shaped interconnecting elements 30curving outward in horizontal planes, attached between the crown portionof the tooth-clasping elements and also between the flange section overthe gum line. It should be noted that the curvature of theinterconnecting elements 30 could be in more than one plane. Thematerials of the tooth-clasping elements 15 and the materials of theinterconnecting elements 30 are preferably of differing materials, withthe interconnecting elements 30 being more flexible. This embodimentcould be easily printed, using a multiple nozzle 3D printer. Theinterconnecting elements 30 would be oriented in a flat horizontal planewith the outer portion of the curve directed away from the teeth (i.e.,toward the cheek on the buccal side attachment and toward the tongue onthe lingual side). Preferably, there are four interconnecting elementsbetween each adjacent pair of tooth-clasping elements, one above theother on both the buccal and lingual sides of the teeth. However, anynumber of interconnecting elements could be used. It is anticipated thatthis embodiment would work well to correct minor rotations and crowding.

This embodiment may also offer the advantage of being less visible thanthe embodiments in FIGS. 1-4 and 11-12. For example, the interconnectingelements 30 can be made of any suitable flexible material including butnot limited to: clear vinyl, clear silicone, and clear urethane, or someother material that is not clear. In the posterior teeth, they do nothave to be clear because they will be seldom seen. If this positioner isfabricated by a 3-D digital printer, the flexible interconnectingelements can be printed simultaneously with the clear tooth-claspingportion.

FIGS. 28 and 29 show an embodiment of a tooth-clasping element 15 thatis pre-loaded to more effectively engage a tooth. This modificationcould be applied to any or all of the previous embodiment disclosedherein. The digital data set corresponding to the shape of the dentalmodel for any particular stage could be modified to move the labialand/or lingual surfaces 13A, 13B of the tooth, found between the levelof the bonded attachment and the gum line, inward toward the center ofthe tooth by a small distance. Then, whether the appliance is printed,or if it is thermoformed over a digitally printed tooth model, theappliance will have a tighter fit along the gum line. Currently,thermoformed positioners have a tendency to become stretched after theyhave been worn for a few days. The material relaxes. The appliancesbecome loose after they have been worn. The modification of the digitalrepresentation of the tooth surface prior to formation of the appliancewill result in a tooth-clasping element that is pre-loaded when it fitsover the full-sized natural tooth, resulting in a tighter fit of theappliance.

In particular, the area of the CAD model located between the bondedattachments and the gum line is modified in the digital filerepresenting the 3-D surface contours of the model. The surfaces 13A and13B representing the portions of the patient's tooth on both the buccaland lingual sides of the tooth from the gingival edge of the bondedattachment to the gum line are moved inward toward the center of thetooth by a distance representing about 1-25% of the thickness of thetooth. When a digital model is made of the tooth upon which to fabricatea thermoformed appliance, or when a 3-D printed appliance is fabricatedwhich does not require the use of a 3D model under it for support forprinting purposes, the corresponding modified surface contours 15A, 15Bin the tooth-clasping element based with the aforementioned areas 13A,13B of the model that were moved inward, will cause the fabricatedappliance to have a pre-load so in these areas, resulting in a tighterfit in these areas. The gum line flange areas will not be affected bythe change in the surface contours, but when the appliance is placed onthe teeth, the real contour of the tooth will force the tooth-claspingelement outward, and the gingival flange area will be forced outwardslightly away from the gum tissue, providing a little more clearance toavoid having the flange region of the appliance impinge on the gumtissue.

FIG. 30 illustrates another embodiment of the present invention havinglonger interconnecting elements 17A and 17B on both the buccal andlingual aspects. The interconnecting elements 17A, 17B extend betweenthe appliance segments 60-62 and skip over one or more teeth. FIGS. 31and 32 show another embodiment of the appliance with longerinterconnecting elements 17 on only the buccal aspect of the appliancesegments.

These embodiments can be used, for example, in cases where we are tryingto intrude incisors. Here, the interconnecting elements 17A, 17B extendfrom the canine over to the central incisor, skipping the lateralincisor. All four incisors are held together as a unit by a singleappliance segment 61, and the remaining teeth on either side of theincisors are held together by two appliance segments 60 and 62. Theseembodiments are primarily intended to overcome the problem duringintrusion where most of the intrusive force is placed on the lateralincisor, and the intrusion force is dissipated somewhat by the time itis transferred to the larger central incisor, which is a larger toothand requires more force to intrude it.

FIGS. 33 and 34 show yet another embodiment of the present inventionhaving longer interconnecting elements 17 between the tooth-claspingelements 15 on individual teeth. These interconnecting elements 17 havea more elongated, irregular shape that allow a greater range of relativemotion between the tooth-clasping elements 15 and their respectiveteeth. In addition, the physical properties of interconnecting elements17 can be individually designed based on their dimensions, shapes andmaterial properties.

FIG. 35 shows the posterior teeth all connected into one tooth claspingelement, extending from the second molar to the cuspid. A flexible clearplastic interconnecting element 17, (there is one on each side with onlythe right side shown in this figure) in this case made of the samecontinuous piece of plastic that forms the rest of the appliance,extends forward and drops down directly above the central incisor toengage a four-unit anterior tooth clasping element that envelopes theincisors, in much the same manner as was shown in FIGS. 33 and 34. Theappliance is activated so that vertical force is directed straight up atthe central incisors.

FIG. 36 shows a similar appliance to FIG. 35, but in this case theactive interconnecting element 17 is made of wire connected to theposterior tooth clasping element. The means of attachment is not shown,but could include all of the methods discussed earlier for attachingwires. The wire has a helical coil near to where it attaches to theposterior tooth clasping element, and the anterior end of the wireextends forward to the four-unit tooth clasping element surrounding theincisor teeth. It is anticipated that the wire will be attached to thefour-unit anterior tooth clasping element in the flange area coveringthe gum tissue above the crowns of the teeth where it will be lessvisible under the upper lip. Preferably, the wire will be attached andwill extend all the way across above the four incisor teeth to the leftside of the mouth where it will be a mirror image of the wire on theright side and will be the active arm on the left side, also containinga helical coil before it is attached to the posterior tooth claspingelement on the left side. The left and right side posterior toothclasping elements will likely be attached together across the palate byany suitable rigid means including clear plastic. The left and rightposterior segments can also be attached to each other across the palateusing a plastic or metal trans-palatal arch or bar.

The above disclosure sets forth a number of embodiments of the presentinvention described in detail with respect to the accompanying drawings.Those skilled in this art will appreciate that various changes,modifications, other structural arrangements, and other embodimentscould be practiced under the teachings of the present invention withoutdeparting from the scope of this invention as set forth in the followingclaims.

We claim:
 1. A tooth-positioning appliance removably securable to apatient's teeth, said appliance comprising: bonded attachments bonded toprotrude from selected teeth; a plurality of tooth-clasping elementsremovably engaging the bonded attachments to attach the appliance toselected teeth, wherein in at least one tooth-clasping element includesa thin shell with a recess for receiving at least one tooth andextending from the lingual aspect, over the occlusal aspect and to thelabial aspect of at least one tooth with opposing lateral edges; and aflexible curved interconnecting element extending between a series ofthe tooth-clasping elements and having curved segments between adjacenttooth-clasping elements.
 2. The tooth-positioning appliance of claim 1wherein the curved interconnecting element extends between the lateraledges of adjacent tooth-clasping elements.
 3. The tooth-positioningappliance of claim 1 wherein the curved interconnecting element extendsadjacent to the patient's gingiva between the tooth-clasping elements.4. The tooth-positioning appliance of claim 1 wherein theinterconnecting element curves toward the patient's gingiva betweentooth-clasping elements.
 5. The tooth-positioning appliance of claim 1wherein the tooth-clasping elements and curved interconnecting elementare fabricated as a single piece.
 6. The tooth-positioning appliance ofclaim 1 wherein the tooth-clasping element further comprises a recessfor receiving and engaging a bonded attachment protruding from a tooth.7. The tooth-positioning appliance of claim 1 wherein the curvedinterconnecting member comprises a wire having curved segments betweenadjacent tooth-clasping elements.
 8. The tooth-positioning appliance ofclaim 1 wherein the tooth-clasping element further comprises a flangeextending over the gum tissue of a patient.
 9. The tooth-positioningappliance of claim 1 wherein the curved interconnecting member comprisesa U-shaped ribbon.
 10. The tooth-positioning appliance of claim 9wherein the curved interconnecting member further comprises areinforcing rib.
 11. The tooth-positioning appliance of claim 1 whereinthe curved interconnecting member further comprises a helical coil. 12.A tooth-positioning appliance removably securable to a patient's teeth,said appliance comprising: attachments adapted to be bonded to protrudefrom selected teeth; a plurality of thin-shelled appliance segments,each having recesses for removably engaging a group of teeth andextending from the lingual aspect, over the occlusal aspect and to thelabial aspect of the teeth with opposing lateral edges; and havingtooth-clasping elements for removably engaging the bonded attachments onselected teeth in said group, to thereby attach the appliance segment tothe selected teeth; and a flexible curved interconnecting elementextending between a plurality of appliance segments with curved segmentsextending between adjacent appliance segments.
 13. The tooth-positioningappliance of claim 12 wherein the curved interconnecting element extendsadjacent to a patient's gingiva between the tooth-clasping elements. 14.The tooth-positioning appliance of claim 12 wherein the curvedinterconnecting member comprises a wire having curved segments betweenadjacent tooth-clasping elements.
 15. The tooth-positioning appliance ofclaim 12 wherein the curved interconnecting element curves toward apatient's gingiva between tooth-clasping elements.
 16. Thetooth-positioning appliance of claim 12 wherein the tooth-claspingelement further comprises a flange extending over the gum tissue of apatient.
 17. A tooth-positioning appliance removably securable to apatient's teeth, said appliance comprising: attachments adapted to bebonded to protrude from selected teeth; a plurality of tooth-claspingelements having a thin shell removably engaging the bonded attachmentsto attach the appliance to selected teeth; said thin shell adapted toextend from the lingual aspect, over the occlusal aspect and to thelabial aspect of at least one tooth with opposing lateral edges; and aflexible curved interconnecting element extending between a plurality oftooth-clasping elements and having curved segments extending between thelateral edges of the tooth-clasping elements adjacent to a patient'sgingiva.
 18. The tooth-positioning appliance of claim 17 wherein thecurved interconnecting member comprises a wire having curved segmentsbetween adjacent tooth-clasping elements.
 19. The tooth-positioningappliance of claim 17 wherein the tooth-clasping element furthercomprises a flange extending over the gum tissue of a patient.
 20. Thetooth-positioning appliance of claim 17 wherein the curved segments ofthe interconnecting element are substantially U-shaped.